This invention relates to methods for inspecting the content of structure modifying additives in molten spheroidal or compacted/vermicular graphite cast iron and the chilling tendency of flaky graphite cast iron.
In manufacturing spheroidal graphite cast iron, magnesium or magnesium based alloys are added into the molten bath of cast iron.
Compacted/vermicular graphite cast iron is one of the most essential materials in industrial casting process and superior in characteristics to spheroidal graphite cast iron.
Properties of these cast irons are characterized by the shape and grain size of graphite and mechanical characteristics thereof depend upon grain size of graphite.
In manufacturing compacted/vermicular graphite cast iron, structure modifying additive which is mainly consisted of magnesium is added into the molten bath of east iron.
In order to manufacture spheroidal or compacted/vermicular graphite cast iron, compositions of the molten bath of cast iron should be inspected by thermal analyzing technique to measure the spheroidizing rate thereof. In the prior art, the molten bath of cast iron is poured into a sampling vessel made of heat resistant material in the form of a small cup with alumel-chromel thermocouple to be connected with an automatic recorder for showing a cooling curve of the sample. Eutectic and supercooling temperatures obtained from the cooling curve are analyzed for determining the spheroidizing rate of graphite.
Where structure modifying additive has not been contained or insufficient to react with the molten bath of cast iron in manufacturing spheroidal or compacted/vermicular graphite cast iron, it is impossible to determine the spheroidizing rate of graphite.
On the other hand, in manufacturing cast iron or flaky graphite cast iron without supplying any structure modifying additive, it is required to make use of chilling effect to cast iron in order to improve the mechanical characteristics. For this purpose, it is necessary to apply the technique for changing the chilling of cast iron and measuring the tendency of chilling.